1. Field of the Invention
The invention relates to a swab-resistant packer device for use in a subterranean well.
2. Brief Description of the Prior Art
During certain operations in a subterranean oil or gas well, such as during a completion or workover procedure, it is commonplace to utilize a packer assembly, bridge plug, or other isolation tool to separate one section or zone of a well from another section or zone. As used herein, the phrase "packer apparatus" includes all such types of tools.
Typically, the packer apparatus will be introduced and/or withdrawn from the well upon a conduit, such as a wireline, cable, or, more particularly, a cylindrical production or workstring through which fluids are introduced and/or withdrawn from the well during certain procedures involved in the completion and/or workover technique. To such conduit is secured at a given location thereon the packing apparatus. The conduit then is introduced into the well concentrically through another cylindrical conduit, which may be casing, or a larger inner diameter production or work string.
The packer apparatus will have an elastomeric sealing element disposed thereon which may be manipulated by hydraulic, mechanical, or electric means to urge the elastomeric seal to expand outwardly into a sealing engagement along the inner diameter of the second or outer conduit, such as the inner smooth wall of casing. In such "set" position, the primary sealing element of the packer apparatus will prevent transmission of fluids there across to isolate one portion of the well from another portion of the well within the annular area defined between the inner diameter of the outer conduit and the outer diameter of the inner conduit.
It is quite desirable to run the packer apparatus into and out of the well as quickly as possible, in order to reduce the time of a trip into and/or out of the hole to thereby reduce labor and other rig costs. In many cases, a trip into or out of a subterranean well with a packer apparatus, as above described, will be delayed because of "swabbing" of the sealing means of the packer apparatus onto the inner diameter of the outer conduit, or casing. Although not fully understood, it is believed that when fluid within the well and carded within the annular area between the inner and outer conduit members rushes over the top of the outsides of the packing seal during movement of the inner, or production or work conduit, it acts similar to an air flow resulting in the presence of a higher velocity fluid on the outside of the packing element and a slower velocity fluid around the interior of such packing element, thus causing a considerable pressure drop that urges the packing element outwardly to form a temporary seal with the wall of the outer conduit. When so sealed, the inner conduit, when moved, swabs or carries fluid with it. This, in turn, results in a substantial reduction in the rate of movement of the production string through the well.
The present invention is directed to abating the problems associated with such "swabbing" problems during insertion or removal of a packer apparatus within a subterranean well.
Applicant is aware of U.S. Pat. No. 4,326,588, entitled "Well Tool Having Knitted Wire Mesh Seal Means And Method Of Use Thereof", and U.S. Pat. No. 4,219,204, entitled "Anti-Extrusion Seals And Packings".